Shader "Prota/Shader-DistanceFog"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _DepthTex ("Depth Texture", 2D) = "white" {}
        _DistanceFrom ("Distance From", float) = 0
        _DistanceTo ("Distance To", float) = 1
        _ColorFrom ("Color From", Color) = (1,1,1,0)
        _ColorTo ("Color To", Color) = (1,1,1,1)
    }
    SubShader
    {
        Cull Off ZWrite Off ZTest Always

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                float2 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;
            };

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = v.uv;
                return o;
            }

            sampler2D _MainTex;
            sampler2D _DepthTex;
            float _DistanceFrom;
            float _DistanceTo;
            fixed4 _ColorFrom;
            fixed4 _ColorTo;

            fixed4 frag (v2f i) : SV_Target
            {
                fixed4 col = tex2D(_MainTex, i.uv);
                float depth = tex2D(_DepthTex, i.uv).r;
                float fog = saturate((depth - _DistanceFrom) / (_DistanceTo - _DistanceFrom));
                float4 fogColor = lerp(_ColorFrom, _ColorTo, fog);
                col = float4((1 - fogColor.a) * col.rgb + fogColor.a * fogColor.rgb, col.a);
                // return float4(fogColor, 1);
                return col;
            }
            ENDCG
        }
    }
}
